Affiliation:
1. Universidade Federal de Viçosa
Abstract
The objective of this study was to optimize and validate the solid-liquid extraction (ESL) technique for determination of picloram residues in soil samples. At the optimization stage, the optimal conditions for extraction of soil samples were determined using univariate analysis. Ratio soil/solution extraction, type and time of agitation, ionic strength and pH of extraction solution were evaluated. Based on the optimized parameters, the following method of extraction and analysis of picloram was developed: weigh 2.00 g of soil dried and sieved through a sieve mesh of 2.0 mm pore, add 20.0 mL of KCl concentration of 0.5 mol L-1, shake the bottle in the vortex for 10 seconds to form suspension and adjust to pH 7.00, with alkaline KOH 0.1 mol L-1. Homogenate the system in a shaker system for 60 minutes and then let it stand for 10 minutes. The bottles are centrifuged for 10 minutes at 3,500 rpm. After the settlement of the soil particles and cleaning of the supernatant extract, an aliquot is withdrawn and analyzed by high performance liquid chromatography. The optimized method was validated by determining the selectivity, linearity, detection and quantification limits, precision and accuracy. The ESL methodology was efficient for analysis of residues of the pesticides studied, with percentages of recovery above 90%. The limits of detection and quantification were 20.0 and 66.0 mg kg-1 soil for the PVA, and 40.0 and 132.0 mg kg-1 soil for the VLA. The coefficients of variation (CV) were equal to 2.32 and 2.69 for PVA and TH soils, respectively. The methodology resulted in low organic solvent consumption and cleaner extracts, as well as no purification steps for chromatographic analysis were required. The parameters evaluated in the validation process indicated that the ESL methodology is efficient for the extraction of picloram residues in soils, with low limits of detection and quantification.
Subject
Plant Science,Agronomy and Crop Science,Physiology,Biochemistry
Reference38 articles.
1. Resolução nº 899, de 29/05/2003. Guia para validação de métodos analíticos e bioanalíticos,2003
2. Adsorption of picloram (4-amino-3,5,6-trichloropicolinic acid) on Panoche, Ephrata, and Palouse soils: a thermodynamic approach to the adsorption mechanism;BIGGAR J. W.;Soil Sci. Soc. Am. Proc.,1973
3. Organic chemicals in the environment dissipation of clopyralid and picloram in soil and seep flow in the Blacklands of Texas;BOVEY R. W.;J. Environ. Qual.,1991
4. Determination of acidic chlorinated pesticides in water: comparison of official EPA method 515. 1 and liquid-solid extraction HPLC/UV and HPLC/PBMS analyses;BRUNER F.;Chromatographia,1996
5. Soil sampling and methods of analysis;CARTER M.R,1993